Recording artist Solange Knowles's iconic personal style has helped her come out from the shadow of sister Beyonce.

Recording artist Solange Knowles's iconic personal style has helped her come out from the shadow of sister Beyonce.

Photo: Bennett Raglin/BET / Getty Images for BET

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Model Agyness Deyn's short, blonde hair and androgynous style inspired Vogue to name her one of the new supermodels in 2007.

Model Agyness Deyn's short, blonde hair and androgynous style inspired Vogue to name her one of the new supermodels in 2007.

Photo: Donato Sardella / WireImage

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Model Karlie Kloss was named by Vogue Paris to be one of the top 30 models of the 2000s.

Model Karlie Kloss was named by Vogue Paris to be one of the top 30 models of the 2000s.

Photo: The Image Gate / Getty Images

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Russian and T.V. host Kseniya Sobchak is often described as "Russia's Paris Hilton."

Russian and T.V. host Kseniya Sobchak is often described as "Russia's Paris Hilton."

Photo: Francois Durand / Getty Images

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Current "it girl" Alexa Chung inspired the Hermes "Alexa" bag—and wrote a book on the topic of "it."

Current "it girl" Alexa Chung inspired the Hermes "Alexa" bag—and wrote a book on the topic of "it."

Photo: Rob Kim / Getty Images

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When Catherine, Duchess of Cambridge, wears something, it sells out worldwide within hours.

When Catherine, Duchess of Cambridge, wears something, it sells out worldwide within hours.

Photo: Max Mumby/Indigo / Getty Images

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Lenny Kravitz's daughter Zoe Kravitz has acted in movies and appeared in fashion campaigns. (Photo by David Livingston/Getty Images)

Lenny Kravitz's daughter Zoe Kravitz has acted in movies and appeared in fashion campaigns. (Photo by David Livingston/Getty Images)

Photo: David Livingston / Getty Images

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Model Cara Delevingne, at 21, has more than 3 million Instagram followers and is known for her bold eyebrows.

Model Cara Delevingne, at 21, has more than 3 million Instagram followers and is known for her bold eyebrows.

Photo: Raymond Hall / FilmMagic

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History's famous 'it girls'

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An apt definition of “it girl” is hard to find.

The term is credited to Rudyard Kipling’s “Mrs. Bathurst” in 1904. “It isn’t beauty, so to speak, nor good talk necessarily,” he wrote. “It’s just ‘It’.” “It” was later popularized in the ’20s, when author’s Elinor Glyn’s novel “It” was made into a movie of the same name starring Clara Bow. She defined “it” as a magnetism—”self-confidence and indifference as to whether you are pleasing or not.”

The definition is fleeting, but the symptoms are consistent: Women want to be them, and men want to bed them. “It girls” come to define the status quo, marching to the beat of their own drum while setting trends, winning friends and gaining legions of imitators in the process.

A modern-day muse, her predecessors include trailblazers and rule-breakers; today, “it” is often personified by fashion and film industry types.

Looking to get a bit of “it” yourself? Browse this slideshow for inspiration, then read the recent guide authored by present-day “it girl” Alexa Chung, boldly titled, simply, “IT.”